The immune response to the HIV involves an "autoimmune" component in which the patient makes both anti-HIV antibody as well as anti-HLA antibody. This type of response has also been observed in other viral infections that cause immune deficiencies. During an HIV infection it appears that the older patients have a more extensive loss of T helper cells and reach low levels of CD4+ cells more rapidly than do younger patients. Younger HIV infected patients experience extended periods in which their CD4+ cell level remains in the normal range.